While SHM science and engineering have matured in recent decades, by now indeed a coherent and well-established branch of structural mechanics, most practicalities are of qualitative nature. The present work suggests a simple, user friendly, method for assessing both damage location and level of damage deterioration along service life.
Setting is within framework of plane stress isotropic elasticity, focusing on a representative configuration of a large plate that contains a hole type damage at a distance from the boundaries, with a-priori unknown location. Health monitoring is based on inducing a remote uniform tension field and measuring strains at selected points. The underlying assumption is that, according to Saint-Venant principle, at sufficient distance from the hole the field characteristics are reasonably approximated by the classical Kirsch solution.
Starting with the simple case of circular hole we show how just a few strain measurements can expose the location of the hole, its radius and possible deterioration (increasing hole diameter). Next, using Inglis and finite element solutions, we turn to more complicated shapes, like elliptic and square holes, and show how the monitoring procedure provides damage location and size of the “equivalent circular hole”. That notion will be examined in some detail, including sensitivities, reliability, and limits of validity. Field strains induced by remote tension have been taken from FE computational analysis or from available analytical solutions.
We shall argue that the predictive power of the suggested method, even though of approximate nature, provides a practical and simple tool of SHM. Possible extension to anisotropic composite material and other types of structural damage plates will be briefly discussed.
